Field of the Invention
The present invention relates to a toner for use in recording methods that use electrophotography, electrostatic recording, electrostatic printing, or toner jet recording.
Description of the Related Art
Copiers and printers have in recent years entered into use in new market sectors, and a high image stability and increases in printing speed are thus being required even for use under diverse environments. For example, printers, which previously have been used mainly in offices, are now also being used under severe environments of high temperature and high humidity. At the same time, additional savings in energy and space are also being required, and it has thus become critical to provide a stable image quality even under these conditions.
Various image-forming methods have been proposed as a consequence. Among these is the so-called jumping method, which uses a magnetic toner and a rotating sleeve having a magnet pole disposed at its center and which uses an electric field to induce jumping between the surface of the photosensitive member and the surface of the sleeve. The jumping method is a developing method that has a high stability and is an effective means for responding to the above-described needs.
However, during, for example, storage in a warehouse, long-term standing may occur under conditions that are more severe than normal, and this can easily cause a deterioration in toner properties. A toner that has experienced such a history is prone to exhibit, for example, an impaired image quality and an impaired durability.
In particular, the decline in the uniformity of charging brought about by toner deterioration results in inaccurate jumping by the toner to the latent image on the photosensitive member, which can produce the problem of causing a decline in the dot reproducibility due to, for example, scattering into areas outside the latent image on the photosensitive member. The phenomenon of this type in particular becomes very prominent under high temperatures/high humidities, which readily produce charge leakage due to the binding of moisture to the toner.
High temperatures/high humidities are also particularly problematic for toner durability. For example, exudation of the release agent (also referred to below as wax) present in the toner is prone to occur. In addition, an acceleration of the deterioration in the durability is prone occur, for example, the external additives on the toner surface are buried.
In order to inhibit toner deterioration in such severe environments, an increase in the hardness can be contemplated in order to raise the heat resistance of the toner; however, raising the hardness alone produces an impaired fixing performance and makes it difficult to balance the developing performance and the fixing performance.
In response to the various problems described above, an example is presented in Japanese Patent Application Laid-open No. H7-092737 (U.S. Pat. Nos. 5,744,276 and 5,942,366) in which the low-temperature fixability and dot reproducibility are stabilized by controlling the molecular weight distribution and viscoelasticity of the toner; however, there is still room for improvement here with regard to further increasing the image stability and durability after standing at high temperature/high humidity.
In addition, an improvement in the fixing performance, e.g., the hot offset and so forth, is pursued in Japanese Patent Application Laid-open No. 2004-177866 by controlling the relaxation modulus during a prescribed stress relaxation and controlling the stress relaxation time at the fixing unit. Again, however, there is still room for improvement here with regard to increasing the image stability and durability after standing at high temperature/high humidity.
An improved low-temperature fixability and an inhibition of image defects are pursued in WO 2009/057807 (US Published Application No. 2009/0197192) by controlling the dispersibility of the magnetic body in a magnetic toner. Again, however, there is still room for improvement here with regard to increasing the image stability and durability after standing at high temperature/high humidity.